Corrosion handbook
6 06/21
1.2 Forms of corrosion
1. 2.1 Uniform corrosion / shallow pitting corrosion
Uniform corrosion removes a metal’s surface almost evenly.
The partial reactions (metal dissolution and oxygen reduction) are statistically
distributed over the surface, leading to a largely homogenous dissolution of the
metal and uniform formation of corrosion products (e.g. red rust on steel).
The extent of this form of corrosion can usually be well estimated on the basis
of previous experience. The rate of corrosion is usually given in micrometers
per year (µm/a). Using these average values, it is possible to estimate the life
expectancy of a component, and thus to enhance its life expectancy by increasing
its thickness. Unprotected carbon steel and zinc-coated steel are materials, which
typically show uniform or shallow pitting corrosion in outdoor environments.
In reality, truly homogenous corrosion attack is unlikely to take place. There are
always areas, especially on complex metal parts, which will corrode faster than
others– leading to a more or less rough surface with an irregular covering of
corrosion products (see Fig. 4).
0RUHQREOH /HVVQREOH
Fig. 4: Corrosion of steel components.